martedì 29 aprile 2014

Ossitocina: il neuropeptide dell’intersoggettività

di Alberto Carrara, LC
Coordinatore del Gruppo di Neurobioetica (GdN)

Che il neuropeptide ossitocina sia una molecola importante per quella dimensione antropologica che denominiamo “intersoggettività”, è noto da diversi anni. Numerosi sono gli studi in merito. Basterebbe digitare il lemma “oxytocin” sul motore di ricerca scientifico PubMed per rendersi conto dell’abbondanza di materiale profuso attorno a questa molecola di soli 9 amminoacidi. Eccovi le cifre alla data odierna: ben 1114 pagine zeppe di 22269 titoli bibliografici riguardanti questo peptide molto antico!

Un recentissimo studio pubblicato su PNAS online ieri, 28 aprile 2014 ed intitolato Inhaled oxytocin increases positive social behaviors in newborn macaques, conferma il ruolo positivo e promotivo di questo neuropeptide nel favorire i comportamenti sociali tra individui della stessa specie.



I ricercatori Elizabeth A. Simpson, Valentina Sclafani, Annika Paukner, Amanda F. Hamel, Melinda A. Novak, Jerrold S. Meyer, Stephen J. Suomi e Pier Francesco Ferrari del Laboratory of Comparative Ethology, Eunice Kennedy Shriver National Institute of Child Health and Human Development del National Institutes of Health, del Dipartimento di Neuroscienze dell’Università di Parma e del Department of Psychology del University of Massachusetts (PNAS. Published online April 28 2014 doi:10.1073/pnas.1402471111), sono partiti dal fatto che sebbene l’ossitocina esogena aumenti effettivamente la socialità nell’adulto, ancora non si avevano dati sullo stesso effetto nei neonati o infanti (Although exogenous oxytocin increases social function in adults—including expression recognition and affiliation—it is unknown whether oxytocin can increase social interactions in infants).

L’ipotesi di lavoro formulata dai ricercatori prevedeva la nebulizzazione di ossitocina a macachi dai 7 ai 14 giorni di vita. In totale, l’esperimento ha coinvolto 28 macachi, in uno studio “in doppio cieco” ossitocina vs soluzione salina (We hypothesized that nebulized oxytocin would increase affiliative social behaviors and such effects would be modulated by infants’ social skills, measured earlier in development. We also hypothesized that oxytocin’s effects on social behaviors may be due to its anxiolytic effects. We tested these hypotheses in a blind study by nebulizing 7- to 14-d-old macaques (n = 28) with oxytocin or saline).

I risultati sono stati sorprendenti. A seguito della somministrazione dell’ossitocina nebulizzata, aumentavano le espressioni facciali degli infanti macachi alle cure di un caregiver umano. Inoltre, gli infanti più propensi ad interazioni sociali positive, risultavano più sensibili all’ossitocina esogena.

L’ossitocina faceva diminuire il cortisolo a livello della saliva, ma non mutava i comportamenti correlati allo stress. Questo suggerisce la possibilità che l’ossitocina abbia un qualche effetto ansiolitico.

Questo studio si caratterizza per essere la prima evidenza sperimentale del ruolo dell’ossitocina nella promozione di comportamenti sociale positivi in neonati (di macaco).

Questo è un dato significativo che consentirà sviluppi ulteriori che permetterà lo sviluppo di strategie terapeutiche in numerosi deficit neonatali di socialità e di interazione interpersonale (To our knowledge, this study provides the first evidence that oxytocin increases positive social behaviors in newborns. This information is of critical importance for potential interventions aimed at ameliorating inadequate social behaviors in infants with higher likelihood of developing neurodevelopmental disorder).

Di seguito riporto, in lingua inglese, il “senso” o razionale dello studio e l’abstract.

Significance
Oxytocin promotes positive social behaviors in several species and therefore may be a therapeutic tool for neurodevelopmental disorders. It remains untested, however, whether oxytocin may affect infants, and whether effects may vary depending on infants’ social skills or interest. To test these predictions, we administered nebulized oxytocin to rhesus macaque newborns. Macaques, like humans, engage in complex face-to-face mother–infant interactions. Oxytocin increased infants’ affiliative communicative gestures and decreased salivary cortisol, and higher oxytocin levels were associated with greater social interest. Infants with stronger imitative skills were most positively influenced by oxytocin, suggesting that oxytocin sensitivity may underlie early social motivation. These results suggest that oxytocin may be a promising early intervention for infants at risk for abnormal social functions.


Abstract

Early caregiver–infant interactions are critical for infants’ socioemotional and cognitive development. Several hormones and neuromodulators, including oxytocin, affect these interactions. Exogenous oxytocin promotes social behaviors in several species, including human and nonhuman primates. Although exogenous oxytocin increases social function in adults—including expression recognition and affiliation—it is unknown whether oxytocin can increase social interactions in infants. We hypothesized that nebulized oxytocin would increase affiliative social behaviors and such effects would be modulated by infants’ social skills, measured earlier in development. We also hypothesized that oxytocin’s effects on social behaviors may be due to its anxiolytic effects. We tested these hypotheses in a blind study by nebulizing 7- to 14-d-old macaques (n = 28) with oxytocin or saline. Following oxytocin administration, infants’ facial gesturing at a human caregiver increased, and infants’ salivary oxytocin was positively correlated with the time spent in close proximity to a caregiver. Infants’ imitative skill (measured earlier in development: 1–7 d of age) predicted oxytocin-associated increases in affiliative behaviors—lip smacking, visual attention to a caregiver, and time in close proximity to a caregiver—suggesting that infants with higher propensities for positive social interactions are more sensitive to exogenous oxytocin. Oxytocin also decreased salivary cortisol, but not stress-related behaviors (e.g., scratching), suggesting the possibility of some anxiolytic effects. To our knowledge, this study provides the first evidence that oxytocin increases positive social behaviors in newborns. This information is of critical importance for potential interventions aimed at ameliorating inadequate social behaviors in infants with higher likelihood of developing neurodevelopmental disorder.

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